Adaptive Thresholding for High Dual-Tone Signal Instantaneous Dynamic Range in Digital Microwave Receiver

A primary concern in the current radar-receiver design involves the critical issue of setting a threshold level that is optimal for all operating conditions. A novel adaptive thresholding technique is presented to maximize both the receiver sensitivity and the dual-tone signal instantaneous dynamic range (IDR) for digital microwave receivers. The additional constraint placed for signal detection improves the false-alarm rate with a minimal firmware increase due to the simplicity of the proposed algorithm. Using our adaptive thresholding technique, the receiver´s maximum IDR varies between 34 and 24 dB below the primary signal for primary-signal strengths between -4 and -32 dBm. Our adaptive thresholding technique was realized in firmware through two receiver designs, i.e., the initial-scaling-stage (ISS) and multistage-scaling (MSS) receiver designs. Both receiver designs show significant improvement in weak-signal spurious-free dynamic range (SFDR) performance. The MSS receiver design shows a nearly 3-dB improvement in weak-signal SFDR performance. Performance evaluations show a well-coordinated effort for adaptive thresholding system integration into the existing radar-receiver system.